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36 Cards in this Set
- Front
- Back
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Nissl body
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elaborate type of rough ER
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neurofilaments
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intermediate filament protein in cytoplasm of nucleus
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ganglia
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cluster of neuron cell bodies in PNS
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nuclei
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cluster of neuron cell bodies in CNS
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tract
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bundle of axons in CNS
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nerve
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bundle of axons in PNS
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axonal terminals
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branches at ends of telondendria which end in bulbous ends that store and release neurotransmitters
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neurilemma
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-aka sheath of schwann
-cytoplams of nucleus of schwann cell squeezed outside the myelin sheath |
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nodes of ranvier
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gaps between myelin
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endoneurium
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delicate CT, covers axon
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perineurium
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coarse CT, covers fasicle
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epineurium
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tough CT, covers nerve/tract
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Biosynthetic Center
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cell body - perikaryon - amitotic
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Receptive Center
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dendrites
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Supporting Cells in CNS
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astrocytes: most abundant, wrap around neurons, involved in forming BBB, regulate brain function
-Microglia: macrophages -Ependymal cells: ciliate columnar cells, line ventricles, circulate CSF -oligodendrocytes: myelinate axons of neurons |
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Supporting Cells in PNS
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-schwann: myelinate axons of neurons
-satellite: surround cell bodies of neurons and control chemical environment |
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Why myelinated axons in CNS can NOT regenerate when severed
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-neurons in CNS: no neurilemma to guide growth of severed axon
-microglia in CNS can't clean up debridement -presence of growth-inhibiting proteins in CNS inhibit regeneration of a severed axon |
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Why axons in PNS CAN regenerate when severed
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-cells of immune system clean up debridement, set stage for regeneration
-regeneration tube: formed by neurilemma of schwann cells that guides regeneration of severed axon |
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Why impulses are conducted faster in larger myelinated axons than in smaller unmyelinated axons
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-large axons transmit impulses at a faster rate because there is less resistance impulse transmission
-myelinated axons use saltatory conduction (jumping) making then faster than unmyelinated axons which use continuous conduction (stepwise) |
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Depolarization Phase
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-entry of sodium ions
-makes membrane potential less negative |
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Repolarization Phase
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-sodium channels close
-potassium channels open -potassium efflux -down toward negative membrane potential |
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Absolute Refractory Period
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-depolarization phase
-sodium channel open -another AP cannot be generated |
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Relative Refractory Period
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-repolarization phase
-sodium channels closed -an exceptionally strong stimulus can cause sodium channels to open for sodium influx leading to depolarization and generation of another AP |
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Mutlipolar Neuron
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1 axon - 2+ dendrites
-most abundant in human body |
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Bipolar Neuron
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1 axon - 1 dendrite
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Pseudounipolar
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1 short process from cell body, bifurcates into a central and peripheral process
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Motor Neuron
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-efferent
-transmits impulses away from CNS to effector organs |
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Sensory Neuron
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-afferent
-transmits impulses from sensory receptors TOWARD CNS |
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Association Neuron
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-interneuron
-in CNS between sensory and motor neurons -99% of neurons in body |
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Group A Nerve Fibers
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-largest diameter
-heavily myelinated -150 m/s |
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Group B Nerve Fibers
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-intermediate diameter
-lightly myelinated - 15 m/s |
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Group C Nerve Fibers
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-smallest diameter
-unmyelinated - 1 m/s |
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Autonomic Nervous System
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-involuntary muscles
-Parasympathetic: increase energy expenditures -Sympathetic: conserve energy expenditures |
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Somatic Nervous System
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-voluntary muscles
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Dilation of Pupils
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-activation of sympathetic nervous system using dilator pupillae muscle
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Constriction of Pupils
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-activation of parasympathetic nervous system using sphincter pupillae muscle
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